The failure mechanism of red layer landslide in Qinghai-Tibet Platean

摘要

Red layer generally represents the stratum that is mainly composed of sandstone, mudstone, siltstone and shale. Landslide existing in red layer is called red layer landslide in geology. Red layer landslide in Qinghai-Tibet Platean consists mostly of the third system mudstone which has special physical and mechanical characteristics. The strength of the third system red layer mudstone in Qinghai-Tibet Platean is much less than that of the red layer mudstone in sichuan and Yunnan; its property of swelling and softening when meeting water is more obvious than that of the red layer mudstone in Sichuan and Yunnan. The red layer landslide region is a 'V' type valley; tectonlsm mainly appear as denudation and cutting; the both sides slopes are comparatively steep; there are many gulch in the slopes. Many fractured zones can be founded in the landslide region; tectonic fissures develop extraordinarily; the rock mass is very crushed. Model test and numerical analysis methods were both used to study the failure mechanism of the red layer landslide in Qinghai-Tibet Platean from several viewpoints including ravine cutting, lateral reloading, earthquake acting and rain water infiltration. The results show that the rock mass relaxing effect due to ravine cutting, strong earthquake and the rock mass softening due to rain water are the main reasons resulting in the development and failure of the landslide. So the failure mechanism of the red layer landslide in Qinghai-Tibet Platean can be described as such a process. Firstly, the region has a original topography (e.g. horizontal ground); then ravine cuts; the rock mass of the slope relaxes due to lateral reloading and the slope begin to deform; the strength of the rock mass decreases for the first time; rain water infiltrates into the slope; the strength of the rock mass decreases for the second time; strong earthquake acts on the slope; finally, the landslide slides in whole.